When leakage of fluid such as water or gas is found in a pipe, it is necessary to specify the position of the pipe where fluid leaks (hereinafter also referred to as a “leak position”) with high precision.
PTL 1 describes a method for specifying a pinhole position of a tubular member. The method described in PTL 1 is such that pressurized gas is charged in the tubular member, and leakage sounds of the gas are detected by sonic sensors mounted at two points spaced away from each other by a certain distance. Further, in the method described in PTL 1, the position of the pinhole in the tubular member is found by comparing sonic waveforms detected by the sensors.